What Is Cellular?

What Are the Differences Between Cellular and Wi-Fi?

Cellular and Wi-Fi are both wireless communication technologies that can transmit data and information without physical connections. To transmit and receive radio waves, cellular relies on base stations, whereas Wi-Fi relies on routing and switching devices such as access points (APs) and wireless access controllers (WACs). Although both technologies use radio waves for data transmission, they use different frequency bands. Cellular mainly uses lower-frequency bands, such as 800 MHz to 2.7 GHz, which are suitable for wide coverage and mobile communication. Wi-Fi mainly uses higher-frequency bands, such as 2.4 GHz, 5 GHz, and 6 GHz, which are suitable for high-speed data transmission and indoor environments. The following table lists the key differences between cellular and Wi-Fi.

What Are the Applications of Cellular?

Devices on networks that are widely dispersed are often connected through physical wired connections. However, there are situations when it is better to connect devices wirelessly due to the reduced cost and added convenience. Such situations include:

• Areas where wired access is costly. Examples include remote branches of enterprises or offshore oilfields.
• Areas where the network is set up temporarily and needs to be adjusted frequently. In such situations, wired access is too costly and provides insufficient mobility. An example is disaster sites.
• Widely distributed sites not fully covered by wired access. Examples include gas stations and ATMs.

In these scenarios, network devices can access a cellular network wirelessly to provide services. This helps meet customer requirements.

As shown in the following figure, branches' egress gateways connect wirelessly to Base Station Subsystems (BSSs). This provides a quick way for the branches and the headquarters to communicate with each other. Another benefit of this is that it gets rid of the heavy workload involved in deploying a wired network. A cellular network consists of the following:

• User device: refers to a device accessing a cellular network. An example is an egress gateway.
• BSS: performs wireless communication with the user device. It contains fixed and mobile base stations of carriers. A BSS is like a converter between wireless and wired networks.
• Transport network and core network: The transport network bears and aggregates data, and the core network processes and routes data.

Basic architecture of a cellular network

How Does Cellular Work?

The cellular function is implemented on a cellular model (such as a router) or cellular card, using a SIM card.

After a SIM card is inserted into the SIM card slot of a cellular router model, or into the SIM card slot on a cellular card which is installed on a router, the router can connect to the carrier network in dial-up mode. After the dial-up function is enabled, the device automatically attempts to establish a dial-up connection with the carrier network without being triggered by data packets. If the dial-up fails, the device automatically tries again at specified intervals. The following figure shows the dial-up connection process.

Dial-up connection process

The process is as follows:

1. The cellular channel interface sends a connection setup request to the cellular modem.
2. The cellular modem sends a connection setup request to the carrier network. The request contains authentication information about the device identity.
3. The carrier network authenticates the device identity. After authentication succeeds, the core network sets up a connection with the cellular modem and assigns an IP address to the modem.
4. The cellular modem instructs the cellular channel interface to go up.
5. The cellular channel interface negotiates with the cellular modem for an IP address, and obtains the IP address assigned by the cellular modem.
6. The cellular channel interface sets up a connection with the carrier network for data service forwarding.